Method of making wash-off relief images



Patented Feb. 13, 1934 1,946,640 PATENT OFFICE METHOD OF MAKING WASH-OFF RELIEF IMAGES Merrill W. Seymour, Irondequoit, N. Y., assignor to Eastman Kodak Company, RochestergN. Y., a corporation of New York No Drawing. Application December 2'7, 1930 Serial No. 505,206

Claims.

This invention relates to photographic sensitive layers adapted to the making of relief images by the wash-off process.

An object of the invention is to provide a sensitive layer for the making of wash-off relief images with which the exposure may be from the emulsion side instead of from the support side as has heretofore been necessary.

A further object is to make the wash-off process adaptable for use on both sides of double coated picture film for a two color motion picture process.

Other objects will appear hereinafter.

The ordinary methods for making wash-off relief images in gelatin, such as carbon printing, or the bleaching of a bromide print with a bichromate solution, require the printing exposure to be made through the support. This is impossible with double coated motion picture film, and is very disadvantageous with other kinds of printing stock, particularly paper.

I overcome this difl'iculty by the use of a specially treated photographic emulsion coating which, from a practical point of view, may be considered as varying in sensitivity throughout its depth, being of greatest sensitivity nearest the support, and of least sensitivity on its upper surface. Such a layer may be described as having topographically graded sensitivity, that is, the sensitivity varies with the distance from the boundary surface. By the method of treatment which I use, this layer may also be considered as possessing topographically graded solubility, as after bleaching it is most soluble on the top surface and least soluble next to the support.

After I have prepared the printing surface in this way, I expose the emulsion in the usual way, from above. After development, the image is densest next to the support and decreasingly dense towards the surface. Thus the highlights in a positive image are visible on the support side only, while the deepest shadows may penetrate to the upper surface. After developingthe the silver halide image, I then submit the silver image to a bichromate bleach, which hardens the gelatin in proportion to the silver present. If the surface is now submitted to the action of warm water, a relief image on the support is obtained. This relief image is next to the support and firmly adheres to it, in distinction from relief images made by previous processes which lie on the surface, when exposed from the emulsion side, the under layer consisting of soluble gelatin. I remove the remaining silver salt with sodium thiosulphate in the usual manner. The resulting transparent relief may be dyed for the purposes of color photography.

The special emulsion or layer of topographically graded sensitivity which I use may be pre- Example An ordinary emulsion maybe treated with a solution applied to 1 its top surface which diminishes either the true sensitivity of the emulsion or the developability of the latent image. This solution is so applied that its action is greatest on the top surface, and diminishes with the depth of the emulsion. A solution which I have used successfully is a 4% solution of potassium iodide. This solution is allowed to act on the emulsion for about 15 seconds, more or less, according to the kind and thickness of the emulsion coating used. 'Fifteen seconds will be satisfactory for an emulsion such as that of regular lantern plates. The emulsion is then washed with running water and dried.

Desensitizing dyes and inorganic oxidizing agents are other useful reagents for this purpose. Substances of this kind are solutions of pinacryptol green, phenosafranin, iodine dissolved in ammonium bromide, chromic acid, and cupric chloride. The desensitizing dyes mentioned are preferably dissolved in '75 to 80% alcohol rather than water, the function of the alcohol being to prevent the gelatin from swelling and thereby limiting the penetration of the solution.

The desensitizing solution may be applied by brushing over the emulsion, by brief immersion, or by overcoating in gelatin. For the latter purpose a solution of gelatin in water and the desensitizer is overcoated on the emulsion, the desensitizing action taking place during the brief period before the gelatin layer dries.

After I have prepared a suitable emulsion surface I carry out the remainder of my invention in the following way. It is understood, of course, that the layer as prepared has been washed, if necessary, and dried. I next expose this sensitive layer from the emulsion side as is usually done. I next develop for about two minutes in a strong developer containing hydroquinone and caustic soda. After development the print is washed for approximately five minutes. It is next bleached in a solution having the following composition, for example:

Use: A 1 part, B 1 part, water 6 parts. It is to be pointed out that my process does not by this invention I follow out the above-described.

process or certain other methods in which a bichromate bleach is used to insolubilize a gelatin layer. The silver reduces the bichromate ions to chromic ions and thus produces a tanned image in situ.

After bleaching, the relief is developed by soaking in water at 110 to 120 F. The print is then fixed in hypo to remove remaining silver halide. It is then washed. It may then be used for any P p se for which a relief image in gelatin is adapted.

In certain cases it is not necessary to use the step of bleaching the silver image with an oxidizing bath such as the bi-chromate bleach illustrated. This would be true in certain instances where the layer is to be used for imbibition printing. To avoid the use of a bleaching bath, I may use for development a so-called tanning developer. Such developers have been well described in the literature. One which is particularly useful is a pyro developer containing very little or no sodium sulfite. Other such developers are hydroquinone or paraminophenol, formulas for which have been published. On developing with a solution of this type the image layer is converted into a layer having topographically graded solubility, being least soluble where there was the most silver. Afterthis step the relief image may be developedby washing off in warm water as described, omitting the bleaching step. Of course it may be followed by the bleaching step; thereby obtaining a particularly highly insoluble image; before dissolving the insolublized gelatin.

For making two color motion picture positives procedure with slight variations only. I use a transparent support having a coating on each side of the type described above. I print one side, for example, from the green separation negative, and the other side from the red separation negative. I then carry out the remaining steps on both sides at once by immersion until I have obtained the finished relief on each side. I then dye each side separately by flotation in dye solutions of complementary colors, thereby obtaining a finished motion picture in color.

The invention has, of course, other uses than for double 'coated motion picture film, as, for example, for a print on paper stock in monochrome. I do not limit myself by the particular examples given.

I consider as included within my invention all variations and equivalents coming within the scope of the appended claims.

What I claim is: r v

'1. The method ofmaking a relief image which comprises printing a light image from the emulsion side on a layer having sensitivity increasing away from such side, producing therefrom an image of graded solubility, said image being least soluble where the sensitivity was greatest, and washing off the more soluble portions of the layer.

2. The method of making a photographic washofi' relief image in a layer carried on a support, the sensitivity of the layer increasing from top to bottom, which comprises printing said layer from the emulsion side and developing the image by washing oi! the soluble portions, leaving the image next to the support and firmly adherent to it.

3. The method of making a photographic washrequire .a bleaching bath containing potassium ferricyanide such as that used in the Ozobrome' oif relief image in a layer carried on a support, the sensitivity of the layer increasing from top to bottom, which comprises printing said layer from the emulsion side, bleaching the silver image, and developing the image by washing off the soluble portions, leaving a relief image next to the support and firmly adherent to it.

4. The method of making a photographic washoff relief image in a layer carried on a support, the sensitivity of the layer increasing from top to bottom, which comprises printing said layer from the emulsion side, developing in a photographic developer, bleaching the silver image in a bath containing an acid, an oxidizing agent and a; soluble halide, developing the relief image by washing off the soluble portions, and fixing to remove remaining soluble halide.

5. The method of making a photographic wash-off relief image which comprises printing from the emulsion side a silver halide layer carried by a support, said layer having sensitivity increasing from top to bottom developing in a photographic developer, bleaching the silver image in a bath containing an acid, an oxidizing agent and a soluble halide to convert the layer into one having topographically graded solubility, developing the relief image by washing off the soluble portion, and fixing to remove remaining silver halide.

6. The method of preparing a photographic layer having topographically graded sensitivity which comprises treating a highly sensitive silver halide other than iodide layer with a solution of oif relief image which comprises printing from the' emulsion side a silver halide layer carried by a support, said layer having sensitivity increasing from top to bottom, developing in a tanning developer, bleaching the silver image in a bath containing an acid oxidizing agent and a soluble halide to convert the layer into one having topographically graded solubility, developing the relief image by washing off the soluble portions, and fixing to remove the remaining silver halide.

9. Method of making a two-color motion picture which comprises exposing to light images from opposite sides a motion picture film having upon each surface a silver halide layer, the sensitivity of which increases from the outer to the inner surface, transforming the latent images thu formed into differentially soluble images and transforming such images into relief images by washing off the soluble portions.

10. A photographic element comprising a support and a layer thereon which has increasing sensitivity from top to bottom and which includes a highly sensitive, silver halide and relatively insensitive silver iodide, the distribution gradient of the sensitive halide increasing, and that of the iodide decreasing, from top to bottom of the layer.

' MERRILL W. SEYMOUR 

